Linkage rod including limited-displacement flexible mechanism

ABSTRACT

A linkage rod including a limited-displacement flexible mechanism has structural robustness and allows easy reduction in weight and size, simple production and easy operation. The linkage rod including at least one limited-displacement flexible mechanism, wherein the limited-displacement flexible mechanism comprises at least one limited-displacement flexible joint which comprises: a flexible member; and at least one bend limitation section which is arranged in parallel with the flexible member so that the bend limitation section limits a bend of the flexible member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a limited-displacement flexiblemechanism which can be used in a linkage rod or a support arrangement.

2. Description of the Related Art

With the increasing market demand for precision technology, a linearmotion actuator providing high precision has become important formachinery requiring precise displacement such asmultiple-degree-of-freedom displacement mechanism, micro-manipulator orthe like. In most cases, such a linear motion actuator uses anelectromechanical or electrohydraulic arrangement which is usuallyprovided for each rod of a six-degree-of-freedom mechanism (so calledHexapod) (see Japanese Patent Unexamined Publication No. JP2013-096574,U.S. Pat. No. 8,978,480 B2). In the hexapod system, each of the six rodsis adjustable to precisely position an object in three dimensionalspace.

A mounting assembly which can correct the position of a device to besupported along six degrees of freedom is disclosed in U.S. Pat. No.6,402,329 B1. The mounting assembly has three mounting devices eachhaving a deformable triangle structure composed of two sides and avariable length arm. Each of the sides includes a friction free hingecomprising a pair of flexible strips which are located in two planesorthogonal to each other.

SUMMARY OF THE INVENTION

However, in the case of a supporting rod with high rigidity and strengthso as to achieve precise positioning, it is necessary to use a pluralityof parts to assemble the machinery, resulting in difficulty inminiaturization and weight reduction. On the other hand, if in the casewhere the flexible strips are employed for a linkage rod as theabove-mentioned mounting assembly, it is difficult to prevent themachinery from breakage under heavy load or severe environments.Accordingly, the existing techniques cannot achieve a light-weight,miniaturized and simply-manufactured hexapod with high precision.

An object of the present invention is to provide a linkage rod includinga novel limited-displacement flexible mechanism which can achievestructural robustness and allows easy reduction in weight and size, andsimple production.

According to the present invention, a linkage rod including alimited-displacement flexible mechanism, wherein thelimited-displacement flexible mechanism comprises at least onelimited-displacement flexible joint which comprises: a flexible membershaped like a plate; and at least one bend limitation section which isarranged in parallel with the flexible member so that the bendlimitation section limits a bend of the flexible member.

According to the present invention, a bipod comprising two linkage rodseach including a limited-displacement flexible mechanism, wherein thelimited-displacement flexible mechanism comprises at least onelimited-displacement flexible joint which comprises: a flexible membershaped like a plate; and at least one bend limitation section which isarranged in parallel with the flexible member so that the bendlimitation section limits a bend of the flexible member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a first example of a linearmotion mechanism used in a support assembly to which alimited-displacement flexible mechanism according to an exemplaryembodiment of the present invention is applied.

FIG. 2 is a plan view illustrating the linear motion mechanism shown inFIG. 1.

FIG. 3 is a diagram showing an operation of the linear motion mechanismshown in FIG. 1.

FIG. 4 is a schematic diagram showing an example of the productionprocess of a linear motion mechanism as shown in FIG. 1.

FIG. 5 is a perspective view illustrating a second example of a linearmotion mechanism used in a support assembly to which alimited-displacement flexible mechanism according to an exemplaryembodiment of the present invention is applied.

FIG. 6 is a plan view illustrating the linear motion mechanism shown inFIG. 5.

FIG. 7 is a diagram showing an operation of the linear motion mechanismshown in FIG. 5.

FIG. 8 is a perspective view illustrating a support assembly using abipod including a limited-displacement flexible mechanism according tothe first exemplary embodiment of the present invention.

FIG. 9 is a perspective view of a bipod including thelimited-displacement flexible mechanism as shown in FIG. 8.

FIG. 10 is a side view of the bipod as shown in FIG. 9.

FIG. 11 is a plan view of the bipod as shown in FIG. 9.

FIG. 12 is an enlarged side view of the limited-displacement flexiblejoint of the bipod as shown in FIG. 9.

FIG. 13 is an enlarged side view of the limited-displacement flexiblejoint as shown in FIG. 12 in the case of being curved in one direction.

FIG. 14 is an enlarged side view of the limited-displacement flexiblejoint as shown in FIG. 12 in the case of being curved in the otherdirection.

FIG. 15 is a side view of the support assembly using thelimited-displacement flexible mechanism as shown in FIG. 8 f.

FIGS. 16A-16D are a schematic side-view structure of the supportassembly as shown in FIG. 8 for explaining operations of the supportassembly.

FIG. 17 is a side view illustrating a hexapod mechanism employing thelimited-displacement flexible mechanism according to the secondexemplary embodiment of the present invention.

FIG. 18 is a perspective view illustrating the hexapod mechanism asshown in FIG. 17.

FIG. 19 is a plan view illustrating the hexapod mechanism as shown inFIG. 17.

FIG. 20 is a plan view illustrating the hexapod mechanism as shown inFIG. 17 in a state such that a mounting base has been removed.

FIG. 21 is a plan view illustrating the hexapod mechanism as shown inFIG. 17 in a state such that both a mounting base and all bipods havebeen removed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A limited-displacement flexible mechanism employed in a linkage rodcomprises at least one limited-displacement flexible joint which iscomposed of: a flexible blade; and at least one bend limitation sectionwhich is arranged in parallel with the flexible blade. The bendlimitation section may include two parts which are engaged with eachother such that one part is rotatable with respect to the other partwithin a limited range of angle in a direction of bending the flexibleblade.

More specifically, a first part of the bend limitation section has aprotrusion provided with a pair of stoppers protruding outside from thefirst part. A second part of the bend limitation section has a recesswhich is rotatably engaged with the protrusion of the first part. Therotation of the first part is limited by one of the stoppers makingcontact with one top edge of the recess depending on a bend of theflexible blade. Preferably, the protrusion of the first part iscylindrically shaped so as to rotate depending on a bending direction ofthe flexible blade.

More preferably, the linkage rod is provided with at least one pair oflimited-displacement flexible joints such that each pair oflimited-displacement flexible joints is allowed to bend in bothdirections orthogonal to each other, respectively. Further preferably,the linkage rod is formed integrally by using any technology includinginjection molding, 3-dimentional printer or MEMS (Micro ElectroMechanical Systems).

A bipod having two linkage rods as described above can be used toassemble a multiple-degree-of-freedom adjustment mechanism whichincludes a base plate, a top plate and a plurality of supportassemblies, each of support assemblies including the bipod and a linearmotion mechanism. The bipod has the two linkage rods, one ends of whichare fixed to each other at a top provided with a support section. Thesupport section moves within a predetermined range on a plane formed bythe linkage rods depending on respective linear motions of the linearmotion mechanism.

1. First Example of Linear Motion Mechanism

Referring to FIGS. 1 and 2, a linear motion mechanism 10 used in amultiple-degree-of-freedom adjustment mechanism employing at least onebipod includes an elliptical ring 101 having a fixed point 102 connectedto a fixed section 103 and a movable point 104 connected to a movablesection 105. The fixed point 102 and the movable point 104 are both endsof the major axis of the elliptical ring 101.

The elliptical ring 101 has soft spring sections 106 a and 106 b whichare fixed respectively to both sides of the elliptical ring 101 in thedirection of the minor axis so that the elliptical ring 101 issandwiched between the soft spring sections 106 a and 106 b. Therespective ends of the soft spring sections 106 a and 106 b are providedwith operating plates 107 a and 107 b. Preferably, the soft springsections 106 a and 106 b have the same spring constant so as to press orstretch the elliptical ring 101 equally. In FIG. 1, the soft springsections 106 a and 106 b are a bellows-like spring, which is merely anexample.

Each of the soft spring sections 106 a and 106 b is preferably composedof two soft springs which are arranged in parallel with each other. Morespecifically, as shown in FIG. 2, the soft spring section 106 a iscomposed of two soft springs 106 a 1 and 106 a 2, which are arranged inparallel and may be symmetric with respect to the minor axis of theelliptical ring 101. The soft spring section 106 b is composed of twosoft springs 106 b 1 and 106 b 2 in the same arrangement as the softspring section 106 a. This two-parallel-spring arrangement enables aself-alignment function with eliminating the effects of misalignment,allowing the movable section 105 to linearly move as intended withoutthe need of pressing or stretching the operating plates 107 a and 107 bperpendicularly to their respective surfaces.

The movable section 105 is supported on both sides thereof by first andsecond elastic supporting sections to ensure linear motion along themajor axis of the elliptical ring 101. One side of the movable section105 is connected to a first elastic supporting section. Morespecifically, the movable section 105 is connected to a movable section110 a through two leaf springs 108 a and 109 a. The movable section 110a is further connected to fixed sections 113 a and 114 a through leafsprings 111 a and 112 a, respectively. In other words, the one side ofthe movable section 105 is connected to the fixed sections 113 a and 114a through a first pair of leaf springs 108 a and 109 a and a second pairof leaf springs 111 a and 112 a. Similarly the other side of the movablesection 105 is connected to the second elastic supporting section suchthat the movable section 105 is connected to the fixed sections 113 band 114 b through a first pair of leaf springs 108 b and 109 b, amovable section 110 b and a second pair of leaf springs 111 b and 112 b.

In this manner, both sides of the movable section 105 are supported bythe first and second elastic supporting sections, respectively so thatthe movable section 105 stably move along the major axis of theelliptical ring 101 without swinging.

In addition, two corners on the one side of the movable section 105 arecut away so that the fixed sections 113 a and 114 a are partly placedwithin the cutaway portions, respectively. Similarly, two corners on theother side of the movable section 105 are cut away so that the fixedsections 113 b and 114 b are partly placed within the cutaway portions,respectively. Accordingly, the movable section 105 is movably sandwichedbetween the fixed sections 113 a and 113 b and between the fixedsections 114 a and 114 b, preventing the motion of the movable section105 from excessive swinging from side to side and its excessivedisplacement in the direction of the major axis of the elliptical ring101 and therefore restricting the motion of the movable section 105within a predetermined range.

As described already, the spring constants of a pair of the soft springsections 106 a and 106 b and two pairs of the leaf springs 108 a and 109a and the leaf springs 111 a and 112 a can be selected appropriately toobtain a desired speed reduction ratio. An operation of the linearmotion mechanism 10 will be described.

Referring to FIG. 3, when the soft spring sections 106 a and 106 b arepressed or stretched in mutually opposite input directions 201 a and 201b, the elliptical ring 101 is deformed as shown by arrows 202 a, 202 band 203 such that the length of the minor axis is reduced or increasedand the length of the major axis is increased or reduced. Since thefixed point 102 is prevented from moving, the movable point 104 moves inthe direction 203, causing the movable section 105 to slightly move inthe output direction 205 while the movable sections 110 a and 110 b alsoslightly moving in the same directions 204 a and 204 b, respectively.

In this manner, by the soft springs 106 a and 106 b pressing orstretching the elliptical ring 101, the elliptical ring 101 iselastically deformed to linearly move the movable section 105 along themajor axis of the elliptical ring 101. The input direction of thepressing/stretching is orthogonal to the output direction of linearmotion of the movable section 105. In the case where the spring constantof the soft spring sections 106 a and 106 b is lower than the springconstants of the elliptical ring 101 and the leaf springs 108 a, 109 a,111 a, 112 a, 108 b, 109 b, 111 b and 112 b, the amount of inputdisplacement applied to the soft spring sections 106 a and 106 b can betransformed to a desired amount of linear motion of the movable section105.

As described above, the linear motion mechanism 10 is allowed to operateon the same flat surface, resulting in enhanced miniaturization andstructural strength as well as easy operation.

As illustrated in FIG. 4, all sections 101-114 of the linear motionmechanism 10 may be formed integrally by cutting its plane structuralshape from a single elastic plate 120 with a homogeneous material havinga predetermined thickness. Accordingly, the linear motion mechanism 10has a two-dimensional structure with all sections 101-114 having thesame thickness, allowing easy reduction in weight and size and simpleproduction. Another technology such as injection molding, 3-dimentionalprinter or MEMS (Micro Electro Mechanical Systems) may be employed forproduction of the linear motion mechanism 10.

According to the above-mentioned linear motion mechanism used in themultiple-degree-of-freedom adjustment mechanism, larger inputdisplacement of the soft spring sections is transformed to smallerlinear motion of the movable section according to a spring constantratio. Accordingly, even whether the input displacement is applied tothe soft spring sections with less precision, the linear motionmechanism can provide linear motion with greater precision. If thespring constant ratio is previously known, the amount of displacement ofthe movable section can be calculated with precision by preciselymeasuring the input displacement of the soft springs without preciselymeasuring the displacement of the movable section. Accordingly, thefirst exemplary embodiment of the present invention can achievenano-resolution motion of the movable section.

In addition, as described above, each section of the linear motionmechanism 10 moves due to the Nature of Motion through the monocoquedesign with homogenous materials and without any passages via slidingmechanisms, resulting in no potential motion losses and achieving thefollowings:

i. Absolutely predictable and repeatable motions;ii. Precise motion without complex position sensors and close-loop servocontrol, therefore enabling an open-loop control;iii. Perfectly working in a wide temperature ranges, cryogenic to theupper 400° C. or even more;iv. Semi-permanent life without the need of considerations of thepressing/stretching mechanisms (input mechanisms);v. Zero particle and zero cross contamination; andvi. High resistance to corrosive conditions such as being submerged inthe corrosive gases and liquid.

2. Second Example of Linear Motion Mechanism

As shown in FIGS. 5 and 6, a linear motion mechanism 20 used in amultiple-degree-of-freedom adjustment mechanism employing at least onebipod is formed by a combination of first linear motion section 300 andsecond linear motion section 400, each of which has the substantiallysame functional structure as the linear motion mechanism 10 as shown inFIGS. 1 and 2. The first linear motion section 300 and the second linearmotion section 400 are arranged such that the major axes of theelliptical rings 301 and 401 are in alignment with each other. The firstlinear motion section 300 and the second linear motion section 400 havea common fixed section 303/403 corresponding to the fixed section 103 ofthe first exemplary embodiment. Accordingly, the linear motion mechanism20 provides movable sections 305 and 405 respectively on its both sides.

More specifically, the first linear motion section 300 includes anelliptical ring 301 having a fixed point 302 connected to a fixedsection 303 and a movable point 304 connected to a movable section 305.The fixed point 302 and the movable point 304 are both ends of the majoraxis of the elliptical ring 301.

The elliptical ring 301 has soft spring sections 306 a and 306 b whichare connected on both sides of the elliptical ring 301 in the directionof the minor axis, respectively. The respective ends of the soft springsections 306 a and 306 b are provided with operating plates 307 a and307 b. Preferably, the soft spring sections 306 a and 306 b have thesame spring constant so as to press or stretch the elliptical ring 301equally. In FIG. 5, the soft spring sections 306 a and 306 b are abellows-like spring, which is merely an example. Each of the soft springsections 306 a and 306 b has the two-parallel-spring arrangement similarto the soft spring sections 106 a and 106 b of the first exemplaryembodiment.

The movable section 305 is supported on both sides thereof by elasticsupporting section to ensure linear motion along the major axis of theelliptical ring 301. The elastic supporting section is similar to thefirst and second elastic supporting sections of the first exemplaryembodiment and therefore the detailed descriptions are omitted. Sincethe respective sides of the movable section 105 are supported by theelastic supporting section, the movable section 305 stably move alongthe major axis of the elliptical ring 301 without swinging.

As described already, the spring constants of a pair of the soft springsections 306 a and 306 b and the elastic supporting section can beselected appropriately to obtain a desired speed reduction ratio.

The structure of the second linear motion section 400 is similar to thatof the first linear motion section 300. In brief, the second linearmotion section 400 includes an elliptical ring 401 having a fixed point402 connected to a fixed section 403 and a movable point 404 connectedto a movable section 405. The fixed point 402 and the movable point 404are both ends of the major axis of the elliptical ring 401. Theelliptical ring 401 has soft spring sections 406 a and 406 b which areconnected on both sides of the elliptical ring 401 in the direction ofthe minor axis, respectively. The respective ends of the soft springsections 406 a and 406 b are provided with operating plates 407 a and407 b. The movable section 405 is supported on both sides thereof byelastic supporting section to ensure linear motion along the major axisof the elliptical ring 401.

As shown in FIG. 7, the operating plates 307 a and 307 b are operated inthe opposite directions, causing the soft springs 306 a and 306 bconcurrently to be pressed or stretched as mentioned in the firstexemplary embodiment. Similarly, the operating plates 407 a and 407 bare operated in the same manner as, but independently of the operatingplates 307 a and 307 b. Accordingly, when the soft spring sections 306 aand 306 b and the soft spring sections 406 a and 406 b are pressed orstretched, the elliptical rings 301 and 401 are deformed to move themovable sections 305 and 405 in the directions 309 and 409,respectively.

In this manner, by the operating plates 307 a and 307 b and theoperating plates 407 a and 407 b elastically deforming the ellipticalrings 301 and 401, respectively, the movable sections 305 and 405 arelinearly moved along the major axis of the elliptical rings 301 and 401.

The direction of pressing/stretching the soft spring sections isorthogonal to the direction of linear motion of the movable sections 305and 405. In the case where the spring constant of the soft springsections 306 a, 306 b, 406 a and 406 b is lower than the springconstants of the elliptical rings 301 and 401 and the elastic supportingsections, the amount of input displacement applied to the soft springs306 a, 306 b, 406 a and 406 b can be transformed to a desired amount oflinear motion of the movable sections 305 and 405. Accordingly, thelinear motion mechanism 20 can provide the advantageous effects similarto the first exemplary embodiment.

Similarly to the first example as shown in FIG. 4, all sections of thelinear motion mechanism 20 may be also formed integrally, for example,by cutting its plane structural shape from a single elastic plate havinga predetermined thickness. Accordingly, it is possible to produce thelinear motion mechanism 20 having a two-dimensional structure with allsections having the same thickness, allowing easy reduction in weightand size and simple production. Another technology such as injectionmolding, 3-dimentional printer or MEMS (Micro Electro MechanicalSystems) may be employed for production of the linear motion mechanism10.

3. First Exemplary Embodiment 3.1) Structure

Referring to FIG. 8, a support assembly using a bipod composed of twolinkage rods according to a first exemplary embodiment of the presentinvention is composed of a bipod 600 and the linear motion mechanism 20as described above. The bipod 600 has two support rods 601 and 602, oneends of which are connected at a top provided with a support section 603to form an upside-down V-shaped bipod. The other ends of the supportrods 601 and 602 are fixed to the movable section 305 of the firstlinear motion section 300 and the movable section 405 of the secondlinear motion section 400, respectively. The support rods 601 and 602have the same structure. Hereinafter, the structure of the support rod601 shown in FIGS. 9-11 will be described as an example.

3.2) Bipod

Referring to FIGS. 9-11, the support rod 601 is shaped like a legincluding a fixed portion 610, two limited-displacement flexible joints611 and 612, a relatively rigid rod 613, and two limited-displacementflexible joints 614 and 615. Each of the limited-displacement flexiblejoints 611, 612, 614 and 615 provides limited flexibility in a directionalternating between orthogonal flexible directions D1 and D2 withrespect to the longitudinal axis of the support rod 601. The flexibledirection D1 is a direction orthogonal to the support rod 601 in a planeformed by the support rods 601 and 602, which is typically illustratedin FIG. 10. The flexible direction D2 is a direction orthogonal to theplane formed by the support rods 601 and 602, which is typicallyillustrated in FIG. 11. In the present example, the limited-displacementflexible joints 611 and 614 are allowed to curve in the direction D2while the limited-displacement flexible joints 612 and 615 are allowedto curve in the direction D1. Accordingly, the support rod 601 canfreely curve in the directions D1 and D2. Similarly, the support rod 602is shaped like a leg including a fixed portion 620, twolimited-displacement flexible joints 621 and 622, a relatively rigid rod623, and two limited-displacement flexible joints 624 and 625 and canfreely curve in orthogonal flexible directions D1 and D2 with respect tothe longitudinal axis of the support rod 602.

However, each of the limited-displacement flexible joints 611, 612, 614,615, 621, 622, 624 and 625 is designed to limit the degree of bending soas to prevent breakage of the joint. The detailed structure of alimited-displacement flexible joint will be described with references toFIGS. 12-14.

Referring to FIG. 12, the limited-displacement flexible joint iscomposed of a flexible blade 630 which is a plate-shaped section with arelatively reduced thickness and a pair of bend limitation sections640L1 and 640L2 which are provided on both sides of the flexible blade630 in parallel to form a single joint. The flexible blade 630 providesflexibility as described above. Each of the bend limitation sections640L1 and 640L2 is composed of two separate parts which are engaged withclearance to rotate around the axis vertical to the paper surface (asindicated by D). More specifically, one of the parts (an upper part) ofthe bend limitation sections 640L1 is composed of a pair of outerstopper L11 and inner stopper L12 protruding from the upper part and acylindrically shaped protrusion L13 provided at the edge of the upperpart. The other of the parts (a lower part) of the bend limitationsections 640L1 is composed of a cylindrically shaped recess L14 which isrotatably engaged with the cylindrically shaped protrusion L13. The bendlimitation sections 640L2 has the same structure as the bend limitationsections 640L1. More specifically, one of the parts (an upper part) ofthe bend limitation sections 640L2 is composed of a pair of outerstopper L21 and inner stopper L22 protruding from the upper part and acylindrically shaped protrusion L23 provided at the edge of the upperpart. The other of the parts (a lower part) of the bend limitationsections 640L2 is composed of a cylindrically shaped recess L24 which isrotatably engaged with the cylindrically shaped protrusion L23.

As shown in FIG. 13, when the support rod bends in the direction 650,the blade 630 also curve in the same direction 650, rotating the upperparts of the bend limitation sections 640L1 and 640L2 with respect totheir lower parts, respectively. The respective rotations cause thestoppers L11 and L22 to be contacted on one top edges of thecylindrically shaped recesses L14 and L24 as indicated by referencenumerals 651 and 652. Accordingly, the rotation of the upper part in thedirection 650 is stopped tightly, preventing breakage of the blade 630.

As shown in FIG. 14, when the support rod bends in the oppositedirection 660, the blade 630 also curve in the same direction 660,rotating the upper parts of the bend limitation sections 640L1 and 640L2with respect to the lower parts, respectively. The respective rotationscause the stoppers L12 and L21 to be contacted on the other top edges ofthe cylindrically shaped recesses L14 and L24 as indicated by referencenumerals 661 and 662. Accordingly, the rotation of the upper part in thedirection 660 is also stopped tightly, preventing breakage of the blade630.

3.3) Operation

Referring to FIG. 15, the support assembly is assembled from the bipod600 and the linear motion mechanism 20. The support rods 601 and 602 arefixed to the movable section 305 of the first linear motion section 300and the movable section 405 of the second linear motion section 400,respectively. Accordingly, the support section 603 of the bipod 600 canbe moved to an arbitrary position within a limited range on a planeformed by the support rods 601 and 602 depending on the respectivedirections and displacements of linear motion of the movable sections305 and 405.

As shown in FIG. 16A, when the operating plates 307 a and 307 b and theoperating plates 407 a and 407 b press the elliptical rings 301 and 401respectively so that the linear motion mechanism 20 moves the movablesections 305 and 405 by the same displacement in the mutually oppositedirections broadening the distance between the movable sections 305 and405, the height of the bipod 600 with respect to the main surface of thelinear motion mechanism 20 is reduced depending on the displacement ofthe movable sections 305 and 405 as indicated by displacement 605perpendicular to the main surface of the linear motion mechanism 20.

As shown in FIG. 16B, when the operating plates 307 a and 307 b and theoperating plates 407 a and 407 b stretch the elliptical rings 301 and401 respectively so that the linear motion mechanism 20 moves themovable sections 305 and 405 by the same displacement in the mutuallyopposite directions reducing the distance between the movable sections305 and 405, the height of the bipod 600 with respect to the mainsurface of the linear motion mechanism 20 is increased depending on thedisplacement of the movable sections 305 and 405 as indicated bydisplacement 605 perpendicular to the surface of the linear motionmechanism 20.

As shown in FIGS. 16C and 16D, when the operating plates 307 a and 307 bpress/stretch the elliptical rings 301 and the operating plates 407 aand 407 b stretch/press the elliptical rings 401 so that the linearmotion mechanism 20 moves the movable sections 305 and 405 in the samedirection by the same displacement, the bipod 600 is moved as it is inthe same direction by the same displacement as indicated by displacement604 parallel to the main surface of the linear motion mechanism 20.

3.4) Production

The bipod 600 including the limited displacement flexible joint asstructured above is made of elastic material with sufficient strengthand may be formed integrally by using any technology such as injectionmolding, 3-dimentional printer or MEMS (Micro Electro MechanicalSystems).

4. Second Exemplary Embodiment 4.1) Structure

Referring to FIGS. 17-21, a hexapod arrangement having six degrees offreedom includes a base plate 701, a top plate 702 and three supportassemblies A, B and C, each of which is composed of the bipod (600A,600B, 600C) and the linear motion mechanism (20A, 20B and 20C) as shownin FIG. 8. The support assemblies A, B and C are fixed and arranged onthe base plate 701 with regular-triangular configuration as typicallyshown in FIG. 20. The top plate 702 is fixed to the support sections ofthe bipods 600A, 600B and 600C. Accordingly, the top plate 702 issupported by three position-adjustable points.

As an example, the base plate 701 is circular and the top plate 702 isstar-shaped. The top plate 702 may be formed of three legs 702A, 702Band 702C joined at a center point with the angle between any twoadjacent legs being 120 degrees. The three legs 702A, 702B and 702C aresupported respectively by the support assemblies A, B and C, astypically shown in FIG. 18. Needless to say, the top plate 702 may becircular. Further, the top plate 702 may be a mounted object requiringfine adjustment, such as optics (e.g. a mirror, prism or lens).

As described already, the linear motion mechanism 20A includes the firstand second linear motion sections 300A and 400A which are capable ofmoving the movable sections 305A and 405A, respectively. Accordingly, asshown in FIGS. 16A-16D, the support section 603A of the bipod 600A fixedon the linear motion mechanism 20A can be moved to an arbitrary positionwithin a limited range on a plane formed by the support rods 601A and602A of the bipod 600A depending on the respective directions anddisplacements of linear motion of the movable sections 305A and 405A. Itis the same with the linear motion mechanisms 20B and 20C.

4.2) Operation

Since the top plate 702 is supported by the support assemblies A, B andC, the position and/or inclination of the top plate 702 can be changedby independently controlling extension, retraction or paralleltranslation of linear motion of at least one of the linear motionmechanisms 20A, 20B and 20C. Hereinafter, typical operations of thehexapod arrangement will be described by referring to FIGS. 16A-16D andFIG. 18 as an example.

As shown in FIG. 16A, when the operating plates 307 a and 307 b and theoperating plates 407 a and 407 b press the elliptical rings 301 and 401respectively so that the linear motion mechanism 20 moves the movablesections 305 and 405 in the broadening directions, the height of a bipod600 is reduced. As shown in FIG. 16B, when the operating plates 307 aand 307 b and the operating plates 407 a and 407 b stretch theelliptical rings 301 and 401 respectively so that the linear motionmechanism 20 moves the movable sections 305 and 405 in the reducingdirections, the height of the bipod 600 is increased. As shown in FIGS.16C and 16D, when the operating plates 307 a and 307 b press/stretch theelliptical rings 301 and the operating plates 407 a and 407 bstretch/press the elliptical rings 401 so that the linear motionmechanism 20 moves the movable sections 305 and 405 in the samedirection by the same displacement, the bipod 600 performs paralleldisplacement. Accordingly, the top plate 702 can be freely moved in sixdirections by a combination of directions and displacements of motionsprovided by the respective linear motion mechanisms 20A, 20B and 20C.

It is assumed that the linear motion mechanisms 20B and 20C are notactivated and only the linear motion mechanism 20A moves the movablesections 305A and 405A by the same displacement in the mutually oppositedirections broadening the distance between the movable sections 305A and405A. In this case, the height of the bipod 600A with respect to themain surface of the linear motion mechanism 20A is lowered, causing thetop plate 702 to be inclined toward the leg 702A. Contrarily, when onlythe linear motion mechanism 20A moves the movable sections 305A and 405Aby the same displacement in the mutually opposite directions reducingthe distance between the movable sections 305A and 405A, the height ofthe bipod 600A with respect to the main surface of the linear motionmechanism 20A is increased, causing the top plate 702 to be inclinedtoward a center line between the legs 702B and 702C.

It is assumed that only the linear motion mechanism 20C is not activatedand the linear motion mechanisms 20A and 20B are activated to move thecorresponding movable sections by the same displacement in the mutuallyopposite directions broadening the distance between the correspondingmovable sections. In this case, both of the heights of the bipods 600Aand 600B are lowered, causing the top plate 702 to be inclined toward acenter line between the legs 702A and 702B. Contrarily, when the linearmotion mechanisms 20A and 20B are activated to move the correspondingmovable sections by the same displacement in the mutually oppositedirections reducing the distance between the corresponding movablesections, both of the heights of the bipods 600A and 600B become higher,causing the top plate 702 to be inclined toward the leg 702C.

It is assumed that only the linear motion mechanism 20C is not activatedand the linear motion mechanisms 20A and 20B are activated to move thecorresponding movable sections by the same displacement in the samedirection. In this case, the top plate 702 is moved and inclined towarda center line between the legs 702A and 702B.

It is assumed that all the linear motion mechanisms 20A, 20B and 20C areactivated to move the corresponding movable sections by the samedisplacement in the same direction, the bipods 600 a, 600B and 600C arerotated, causing the top plate 702 to be rotated in the same directionby the same displacement.

The hexapod arrangement can perform fine adjustment of the top plate 702other than the above-mentioned operations by independently controllingthe linear motion mechanisms 20A, 20B and 20C.

4.3) Advantageous Effects

As described already, according to the linear motion mechanism used inthe multi-degree-of-freedom adjustment mechanism employing a bipodcomposed of two linkage rods according to a second exemplary embodimentof the present invention, larger input displacement of the soft springsections is transformed to smaller linear motion of the movable sectionaccording to a spring constant ratio. Accordingly, even whether theinput displacement is applied to the soft spring sections with lessprecision, the hexapod system employing the linear motion mechanisms canmove the top plate with greater precision. If the spring constant ratiois previously known, the amount of displacement of the top plate can becalculated with precision by precisely measuring the input displacementwithout precisely measuring the displacement of the top plate.

5. Other Applications

The present invention can be applied to high-precision measurementapparatus such as six-degree-of-freedom adjustment device which can besubject to various severe environments, such as aircrafts, spaceshipsand the like.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Theabove-described exemplary embodiment and examples are therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims ratherthan by the foregoing description, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein.

1. A linkage rod including a limited-displacement flexible mechanism,wherein the limited-displacement flexible mechanism comprises at leastone limited-displacement flexible joint which comprises: a flexiblemember shaped like a plate; and at least one bend limitation sectionwhich is arranged in parallel with the flexible member so that the bendlimitation section limits a bend of the flexible member.
 2. The linkagerod according to claim 1, wherein the bend limitation section comprisesa first part and a second part which are engaged with each other suchthat the first part is rotatable with respect to the second part withina limited range of angle in a direction of bending the flexible member.3. The linkage rod according to claim 2, wherein the first part has aprotrusion provided with a pair of stoppers protruding outside from thefirst part, wherein the second part has a recess which is rotatablyengaged with the protrusion of the first part, wherein rotation of thefirst part is limited by one of the stoppers making contact with one topedge of the recess depending on a bend of the flexible member.
 4. Thelinkage rod according to claim 3, wherein the protrusion iscylindrically shaped.
 5. The linkage rod according to claim 1, whereinat least one pair of limited-displacement flexible joints is providedsuch that each pair of limited-displacement flexible joints bend in bothdirections orthogonal to each other, respectively.
 6. The linkage rodaccording to claim 1, wherein the linkage rod is formed integrally byusing any technology including injection molding, 3-dimentional printeror MEMS (Micro Electro Mechanical Systems).
 7. The linkage rod accordingto claim 1, wherein the flexible member is placed between two bendlimitation sections so that the two bend limitation sections limits abend of the flexible member.
 8. A bipod comprising two linkage rods eachincluding a limited-displacement flexible mechanism, wherein thelimited-displacement flexible mechanism comprises at least onelimited-displacement flexible joint which comprises: a flexible membershaped like a plate; and at least one bend limitation section which isarranged in parallel with the flexible member so that the bendlimitation section limits a bend of the flexible member.
 9. The bipodaccording to claim 8, wherein the bend limitation section comprises afirst part and a second part which are engaged with each other such thatthe first part is rotatable with respect to the second part within alimited range of angle in a direction of bending the flexible member.10. The bipod according to claim 9, wherein the first part has aprotrusion provided with a pair of stoppers protruding outside from thefirst part, wherein the second part has a recess which is rotatablyengaged with the protrusion of the first part, wherein rotation of thefirst part is limited by one of the stoppers making contact with oneedge of the recess depending on a bend of the flexible member.
 11. Thebipod according to claim 8, wherein the bipod is formed integrally byusing any technology including injection molding, 3-dimentional printeror MEMS (Micro Electro Mechanical Systems).
 12. The bipod according toclaim 8, wherein the flexible member is placed between two bendlimitation sections so that the two bend limitation sections limits abend of the flexible member.